In an existing communications system, a device that receives data (referred to as receiving end hereinafter) performs check on received data, and feeds back a negative acknowledgement (NACK) to a device that transmits data (referred to as transmitting end hereinafter) when it finds out that an error occurred on a received code block in a transport block. After receiving the NACK feedback information, the transmitting end retransmits the entire transport block. This causes a waste of air interface resources.